chore: simplify return type

Tested with `require('internal/test/binding').internalBinding('util').guessHandleType(2**31)` (not sure if there was a better way, but it works so)

Author: vladfrangu

lib/internal/util.js

@@ -877,15 +877,14 @@ function getCIDR(address, netmask, family) {
 }
 
 const handleTypes = ['TCP', 'TTY', 'UDP', 'FILE', 'PIPE', 'UNKNOWN'];
-setOwnProperty(handleTypes, -1, null);
 
 function guessHandleType(fd) {
   if (typeof fd !== 'number' || fd >> 0 !== fd || fd < 0) {
     throw new ERR_INVALID_FD(fd);
   }
 
   const type = _guessHandleType(fd);
-  return handleTypes[type];
+  return handleTypes[type] || type;
 }
 
 class WeakReference {

src/node_util.cc

@@ -228,10 +228,9 @@ static void GuessHandleType(const FunctionCallbackInfo<Value>& args) {
   int fd;
   if (!args[0]->Int32Value(env->context()).To(&fd)) return;
 
-  // If the provided file descriptor is not valid, we return `-1`, which in JS
-  // land will be marked as null
+  // If the provided file descriptor is not valid, we return null
   if (fd < 0) [[unlikely]] {
-    args.GetReturnValue().Set(-1);
+    args.GetReturnValue().Set(v8::Null(env->isolate()));
     return;
   }